The present invention relates to metal forming dies and the like, and in particular to a stock ejector assembly and associated method incorporating a unique stock ejector assembly.
Metal forming dies, such as stamping dies and the like, are well known in the art. Progressive metal forming dies are unique, very sophisticated mechanisms which have multiple stations or progressions that are aligned longitudinally, and are designed to perform a specified operation at each station in a predetermined sequence to create a finished metal part. Progressive stamping dies are capable of forming complex metal parts at very high speeds, so as to minimize manufacturing costs.
Heretofore, the dies used in metal forming presses have typically been individually designed, one-of-a-kind assemblies for a particular part, with each of the various components being handcrafted and custom mounted or fitted in an associated die set, which is in turn positioned in a stamping press. Not only are the punches and the other forming tools in the die set individually designed and constructed, but the other parts of the die set, such as stock lifters, guides, end caps and keepers, cam returns, etc., are also custom designed, and installed in the die set. Current die making processes require carefully machined, precision holes and recesses in the die set for mounting the individual components, such that the same are quite labor intensive, and require substantial lead time to make, test and set up in a stamping press. Consequently, such metal forming dies are very expensive to design, manufacture and repair or modify.
A liquid, such as a lubricant, mill oil or water may be used on the stock and one or more of the die parts to decrease the wear on the die parts and/or damage to the stock. When a liquid is used on the stock or upper and/or lower die parts of a metal forming die, the stock has a tendency to stick to the die parts. Thus, something must be done to break the lubricant tension/adhesion on the stock so that it can be removed from that portion of the die. In addition, tension/adhesion can also exist between the stock and flat surfaces on the dies whether or not a liquid is used with the stock and/or dies. Such adhesion between flat surfaces also requires the breaking of the developed tension. One way of breaking the tension is to use a threaded spring plunger. This is a self-contained assembly that includes a very small diameter spring which is prone to fail quickly due to its size. When the threaded spring plunger fails, it is a hassle for stampers as they have to continuously replace the threaded spring plungers. Another problem is that the threaded spring plungers typically have a pointed tip that can leave a mark on the stock if the spring pressure is too great.
FIGS. 18-21 illustrate two well-known prior art assemblies. For example, FIG. 18 illustrates the upper die member 72 of a die set with spring plungers 140. The spring plunger 140 includes a spring portion and a tip 146. The spring is received in an aperture 142 in the die member 72 such that the threaded surface 144 of the aperture 142 corresponds to the contours of the spring plunger 140. Such spring plungers 140 typically fail due to the small spring, which effects the overall lifespan of the spring plunger. The tip 146 has a small contact point that can mark the stock material. In addition, due to the small surface area of the tip 146, the spring plunger 140 can have trouble breaking the lubricant tension/adhesion on the stock strip. As illustrated in FIG. 18, the insertion of spring plunger 140 into die member 72 can be a difficult assembly, as the aperture 142 needs to be threaded 144 to correspond to the shape of the spring plunger 140.
Another example of the prior art includes ejector pin assemblies 148, as shown in FIGS. 20 and 21. The ejector pins 148 include a pin 151 with a tip 152 that extends through a hole 157 in the bottom surface 161 of the die member 72. Another hole 158 includes a threaded portion 156 that mates with a set screw 154 of the ejector assembly 148. A spring 150 is received in hole 158 in between the set screw 154 and the head 160 of the pin 151. The spring 150 pushes the head 160 of the pin 151 such that the tip 152 of the pin 151 can extend from the underside 161 of the die member 72. Use of the ejector pins 148 requires costly machining as the die member 72 must receive several small parts. Small holes must be drilled for the pin 151 of the ejector pin assembly 148. The die member 72 has to be counter-bored and tapped for the set screw 154. In addition, the components of the ejector pin assemblies 148 are small components and require an immense amount of time to assemble.
The need for an improved stock ejector thus stems from the issues that metal stamping producers and die shops have long had when creating an “oil breaker” setup in their dies. The improved stock ejector addresses two main items that are currently problematic: The first is that it utilizes a large spring, which provides a much longer product life than a traditional spring plunger. The large spring is on the “exterior” of the assembly and the other construction methods are internal. This design provides the ability for a large spring to be used while keeping the overall footprint of the assembly as small as possible. The second is the increase in surface area that makes contact with the stock. Typical plunger “point” style on spring plungers have very little surface area, and most commonly used are the points that are rounded/spherical. This provides very little contact with the stock and it can leave a “mark” if the spring pressure compared to the contact surface area on the stock are not proper. The improved stock ejector utilizes a “ring” style stripper, which provides more overall surface area in contact with the stock. This amount of contact surface area prevents the stock from being “marked” but is also not so high that the stock wants to stick to it.
Thus, a product that solves these problems would be advantageous and is described herein.